Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 150534
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1134 PM CST Tue Nov 14 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 330 PM CST Tue Nov 14 2017

Latest sfc analysis was indicating sfc wave and warm front
organizing acrs the northern plains and acrs western IA/Northwestern
MO ATTM, while a low stratocu deck with embedded drizzle cloaked the
local area this afternoon. Aloft, looking on the latest water vapor
loop, tonight`s rain-maker wave was noted upstream acrs the
northwestern high plains/WY, with long fetch mid and upper level
moisture feed streaming in from the west-southwest off the coast of
southern/central CA. After this system exits Wed and a brief
following cool down, another stronger system will bring milder air
and more rain chances by Friday.

&&

.SHORT TERM...(This Evening through Wednesday)
ISSUED AT 330 PM CST Tue Nov 14 2017

Tonight...Increasing lift and especially the top-down saturation of
the ongoing dry low to mid levels will switch the drizzle regime
into more of a showery one from the west and southwest after 10 PM
CST and especially midnight. Until then, areas of drizzle or a fine
light rain will continue, with some areas of fog in pre-warm frontal
llvl convergent zone in the far northwestern CWA and eastward along
the HWY 20 corridor to at least DBQ. Currently don`t feel there will
be widespread dense fog enough/limited coverage to support a fog
advisory, but the next shift will have to watch and at least a
special Wx statement may be needed for these areas. Will bank on
rather brisk mixing south to southeasterly sfc flow will combat true
dense fog formation.

Shower-rain coverage really increases after midnight ahead of
incoming sfc front, with mid layer 6.5 C/Km lapse rates and MUCAPES
of 200-400 J/KG supporting isolated to sctrd embedded thunderstorms
from just before midnight through 4-5 AM CST or so, with all but
maybe the northwestern third of the DVN CWA at risk for some late
night rumbles if the progged mid layer instability plume is correct.
Pea size hail possible with the more organized cells. Rainfall
amounts for most areas should measure 0.15 of an inch or less by Wed
morning, although a few areas may get up to a quarter inch. Where
the rain wane after midnight, could see transient areas of fog
developing and will mention at least patchy coverage acrs much of
the CWA into Wed morning. Some localized dense fog possible in
convergent axis of incoming front with temporary wind decrease in
these areas...best chance in the northwest and north central into
Wed morning before post-frontal west to northwest winds increase.

Wednesday...Will walk out lingering rain out of the east and
southeast by 14-15z or so, and may even move out quicker. Again some
temporary fog possible in the frontal transition zone of the north
until post-frontal winds increase. In-building high pressure and
deepening scouring effect of northwest winds will hopefully
translate into some sunshine by afternoon. Wrap around instability
CU possible in the far north as the afternoon progresses. Northwest
winds will look to increase to 15 to 25 MPH with higher gusts in the
fcst sounding deep mixing profiles. The deep mixing to also
translate to high temps at or even a bit above normal despite
switching over to a coll air advection regime...as long as we get
some midday and afternoon insolation.   ..12..

.LONG TERM...(Wednesday Night through next Tuesday)
ISSUED AT 330 PM CST Tue Nov 14 2017

Forecast focus on storm system late this week and into the weekend.

Wednesday night through Thursday night: High pressure will be over
the cwa during this period, then shifting to our east by Thursday
night. The models have slowed the arrival of moisture compared to
previous runs so now Thursday night looks dry also.

Friday through Saturday: Models similar in taking a track similar to
what the ECMWF had all along. That is, from KS to extreme se IA and
then into southern lower MI. The global models are also not as
intense on the cyclone compared to previous runs. The track of the
surface low and weaker solution will limit any thunderstorm chances
as well as any severe potential, as temperatures will be cooler due
to extensive cloud cover and rain.  SPC has completely removed the
severe probability from the map. On Saturday windy and much cooler
with any lingering rain ending in the morning from west to east.
Models suggest the moisture shifting off to our east before the
colder air arrives. Therefore, I don`t see snow as being an issue
with this system. Wind gusts look to be in the 30 to 35 mph range on
Saturday.

Sunday into early next week: The GFS is still the colder solution
with a much more amplified pattern. The GFS has 850 mb temperatures
dipping to -14c into northeast IL by 12z Sunday, while the ECMWF has
-8c. High pressure will be over the cwa on Sunday with highs in the
30s to lower 40s with plenty of sunshine. Early next week highs will
be in the 40s as the high shifts to our east.

Haase

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday Night)
ISSUED AT 1130 PM CST Tue Nov 14 2017

A weak cold front will pass Wednesday mid morning. Until then, expect
MVFR to IFR conditions with periods of mostly light fog, rain and drizzle.
South winds of 5 to 15 mph will shift to the northwest at 15 to 25+
mph with clearing skies by late morning. Winds will diminish to 5 to
10 mph by evening.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...Haase
AVIATION...Nichols



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